The right ventricle (RV) is a complex structure designed as a volume pump. It is roughly pyramidal-shaped and forms most of the anterior surface and inferior border of the heart. Clinically, it has trabeculated inlet and apical portions and a much less trabeculated outlet portion. The trabeculations tend to be coarser and straighter than those in the left ventricle (LV). A moderator band containing the right bundle branch of the conduction system crosses the RV chamber from the septum to the free wall.After birth, the RV pumps blood into the very low resistance pulmonary bed. Pulmonary resistance is usually about 1/10 to 1/15 that of the systemic resistance. The RV is thin-walled and meant for volume not pressure work. It shares the interventricular septum with the LV, but effectively the septum belongs to the LV. The normal curvature of the septum is toward the RV, and the RV pushes in a bellows-like manner against the septum to propel the blood forward.RV contraction is complex, with several motions happening nearly simultaneously. During systole, chordae attached to the trabeculated RV and to the papillary muscles pull the tricuspid valve toward the RV apex, while the RV free wall contracts and pushes the free wall toward the interventricular septum. During LV contraction, the septum firms and increases the septal curvature toward the RV, thus assisting the RV in its bellows action as the RV contracts from it apex toward the pulmonary valve. The RV outflow contracts last in the sequence, creating a milking motion during the RV systolic cycle. The low resistance in the pulmonary vascular system results in blood continuing forward even as the RV initiates diastole, something akin to the RV acting as a fall-away jump shot in basketball. This continued forward flow results in delayed closure of the pulmonary valve (hangout) and is responsible for the splitting of the second heart sound (P 2 following A 2 ).When RV volume overload occurs, the RV chamber becomes more spherical and the curvature of the septum may bow toward the LV during diastole. Thus, when the LV contracts, the septum rounds up again, and paradoxical systolic motion of the septum toward the RV is evident. During RV pressure overload, the normal bowing of the septum toward the RV may be lost as well, and interventricular septal flattening may be seen.The unusual shape of the RV makes estimating RV volumes by angiographic methods difficult to derive, despite numerous past efforts to model it [1]. Indeed, the unusual contractile motion of the RV complicates even the visual estimate of RV contractile function. Reedy and Chapman [2] first attempted to measure RV volumes by applying Simpson's rule to the entire heart then removing the LV and interventricular septum (Fig. 1). Modifications to Simpson's rule have subsequently been proposed [3,4]. Other methods have assumed an ellipsoid shape to the RV (much like the LV) and utilized the area-length method (Fig. 2) [5], have concluded that the body of the RV is an ellipsoid shape but the outflow is
